Simulations of the formation and evolution of isolated dwarf galaxies
Simulations of the formation and evolution of isolated dwarf galaxies
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孤立矮星系形成和演化的模拟
DOI：
10.1111/j.1365-2966.2011.19083.x
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发表时间：
2008
影响因子：
4.8
通讯作者：
H. Dejonghe
中科院分区：
文献类型：
--
作者：
S. Valcke;S. D. Rijcke;H. Dejonghe
我们提出了新的完全自洽的孤立矮星系（DG）的形成和演化模型。我们使用了公开可用的N体/平滑粒子流体动力学（SPH）代码HYPENDIX，其中我们添加了一组星星形成标准，以及化学富集的处方[考虑到Ia型超新星（SN Ia）和II型超新星（SN II）的贡献]，超新星反馈和气体冷却。我们广泛地测试了这些处方的合理性和模型的数值收敛性。该模型遵循一个最初均匀的气体云坍塌在预先存在的暗物质（DM）晕的演变。这些简化的初始条件支持的合并树孤立DG从milli-Millennium模拟提取。模型星系的星星形成历史（SFH）表现出类似爆发的行为。这些爆炸是气体喷出和随后的气体下降的结果。永久离开星系的气体量很小，绝对数量在3 x 10（7）和6 x 10（7）M之间（圆点）。然而，对于质量最小的模型，这超过了其初始气体质量的80%。在大质量模型中，气体密度的局部波动足以引发恒星爆发，或者在小质量模型中，抑制任何超过小残留星星形成（SF）的东西。在这些恒星爆发之间，可能有几个千兆年的时间间隔。
模式的表面亮度轮廓与Sersic轮廓拟合良好，模式的Sersic参数与亮度的相关关系与观测结果一致。我们还比较了模型预测的半光半径R（e），中心速度色散σ（c），宽带颜色B - v，金属丰度[Z/Z（圆点）]与光度的关系和相对于基本平面的位置与现有数据。模型DG的性质与观测DG的性质吻合得很好。然而，大多数质量模型的性质偏离了观测到的星系。这很可能表明星系合并开始影响这个质量区域（M大于或接近10（9）M（圆点））的星系SFH。
我们发现，R（e）和sigma（c）的组合提供了一种评估模型可靠性的好方法。这些被复制的要求同时对SF的空间分布以及DM晕相对于恒星的形状和范围提出了严格的约束。
We present new fully self-consistent models of the formation and evolution of isolated dwarf galaxies (DGs). We have used the publicly available N-body/smoothed particle hydrodynamics (SPH) code HYDRA, to which we have added a set of star formation criteria, and prescriptions for chemical enrichment [taking into account contributions from both Type Ia supernova (SN Ia) and Type II supernova (SN II)], supernova feedback, and gas cooling. We extensively tested the soundness of these prescriptions and the numerical convergence of the models. The models follow the evolution of an initially homogeneous gas cloud collapsing in a pre-existing dark matter (DM) halo. These simplified initial conditions are supported by the merger trees of isolated DGs extracted from the milli-Millennium Simulation. The star formation histories (SFHs) of the model galaxies exhibit burst-like behaviour. These bursts are a consequence of the blow-out and subsequent in-fall of gas. The amount of gas that leaves the galaxy for good is found to be small, in absolute numbers, ranging between 3 x 10(7) and 6 x 10(7) M(circle dot). For the least massive models, however, this is over 80 per cent of their initial gas mass. The local fluctuations in gas density are strong enough to trigger starbursts in the massive models, or to inhibit anything more than small residual star formation (SF) for the less massive models. Between these starbursts there can be time intervals of several gigayears.
The models' surface brightness profiles are well fitted by Sersic profiles and the correlations between the models' Sersic parameters and luminosity agree with the observations. We have also compared model predictions for the half-light radius R(e), central velocity dispersion sigma(c), broad-band colour B - v, metallicity [Z/Z(circle dot)] versus luminosity relations and for the location relative to the fundamental plane with the available data. The properties of the model DGs agree quite well with those of observed DGs. However, the properties of the most massive models deviate from those of observed galaxies. This most likely signals that galaxy mergers are starting to affect the galaxies' SFHs in this mass regime (M greater than or similar to 10(9) M(circle dot)).
We found that a good way to assess the soundness of models is provided by the combination of R(e) and sigma(c). The demand that these are reproduced simultaneously places a stringent constraint on the spatial distribution of SF and on the shape and extent of the DM halo relative to that of the stars.